Eutrophication indicators PSA & EUTRISK The eutrophication concept for coastal shallow waters PSA = Physically Sensitive Areas to eutrophication 3D hydro-dynamical modelling Bottom layer physics High nutrient concentration High phytoplankton biomass Surface layer physics Pressure Effect Impact Supporting factors Oxygen deficiency EUTRISK = Eutrophication Risk index Remote sensing of Ocean Colour In black = the eutrophication concept In red = the inputs In blue = the outputs = indicators Jean-Noël DRUON

Eutrophication indicators PSA & EUTRISK Monthly mean of the selected physical variables for areas <100m Surface advection Stratification Monthly mean (solid) and standard deviation (dashed) of the selected physical variables for the Adriatic Sea (left) and the North Sea (right) for waters shallower than 100 m: a) mean advection of the mixed layer or residual current in case of tides (m s-1), b) maximum of the vertical density gradient estimated from mean daily profiles (kg m-4), and c) mean diffusivity coefficient near the sea floor (m2 s-1). Bottom Friction Adriatic Sea North Sea

Eutrophication indicators PSA & EUTRISK The stratification index,C_strat Adriatic Sea North Sea Comparison of the stratification index, C_strat, in a) the Adriatic Sea and b) the North Sea (right) from January to December.  

Eutrophication indicators PSA & EUTRISK The advection and bottom friction indices, C_adv and C_kz_b (August) Adriatic Sea North Sea Bottom Friction Advection Comparison of the spatial distribution of a) the advection index, C_adv, and b) the bottom diffusity index, C_kz_b, in the Adriatic Sea (left) and North Sea (right) for August.

Eutrophication indicators PSA & EUTRISK The conceptual model Surface Physics = Potential primary production (C_adv + C_strat)/2 (C_kz_b + 0.5*C_oxy_sat)/1.5 Dominant factors PSA Bottom diffusivity High  Low = Oxygen availability Bottom Physics No  Stratification Yes  (C_kz_b + C_oxy_sat + C_strat + C_adv)/4 (C_kz_b + C_oxy_sat + C_strat + C_blt)/4 EUTRISK Following the principle of the dominant factor, three formulations of the bottom physics index are used () ; the numbers allocated to each index indicate their use in C_phys_bott. C_kz_b is the bottom diffusivity index, C_oxy_sat is the oxygen saturation index, C_strat is the stratification index, C_adv is the advection index and C_blt is the benthic layer thickness index. Surface phytoplankton biomass Advection = Oxygen consumption Organic matter

Eutrophication indicators PSA & EUTRISK April August Adriatic Sea North Sea The oxygen saturation index,C_oxy_sat Comparison of the spatial distribution of the oxygen saturation index, C_oxy_sat, in the Adriatic Sea (left) and North Sea (right) for April and August computed from near bottom monthly means of temperature and salinity. Depths beyond 100 m are not calculated. South-West of Italy, West Channel and West of UK are not areas covered by the models.

Eutrophication indicators PSA & EUTRISK The benthic layer thickness index,C_blt August Adriatic Sea North Sea TOP: Variation of the benthic layer thickness index function of the depth difference between the sea bottom and the pycnocline (C_blt  1). BOTTOM: Comparison of the spatial distribution of the benthic layer thickness index, C_blt, in the Adriatic Sea (left) and North Sea (right) for August. Depths beyond 100 m are not calculated. South-West of Italy, West Channel and West of UK are not areas covered by the models.

Eutrophication indicators PSA & EUTRISK High Medium Low Sensitivity April August December Adriatic Sea North Sea The bottom physics index, C_Phys_bott Or, where is the physical critical availability of oxygen near the bottom (supposing a uniform input of organic matter). Comparison of the bottom physics index, C_Phys_bott, in a) the Adriatic Sea and b) the North Sea (right) in April, August and December. This index represents the physical availability of oxygen near the sea bottom (low towards red).

Eutrophication indicators PSA & EUTRISK High Medium Low Sensitivity April August December Adriatic Sea North Sea The surface physics index, C_Phys_surf Or, where are the favourable physical conditions for the phytoplankton growth (supposing a uniform nutrient distribution). Comparison of the surface physics index, C_Phys_surf, in a) the Adriatic Sea and b) the North Sea (right) in April, August and December. This index represents the favourable physical conditions for the phytoplankton growth (towards red).

Eutrophication indicators Physically Sensitive Areas to eutrophication PSA High Medium Low Sensitivity Adriatic Sea North Sea April August December Or, where would be the bottom oxygen deficiencies with a uniform nutrient distribution and primary production. The Physically Sensitive Area index to Eutrophication (PSA), based on 3D hydrodynamic modelling data (mainly advection, stratification and bottom friction), reveals how different is the physical resistance of coastal European regions to the eutrophication phenomena due to the diverse physical conditions. Note the spatial and temporal variability. In black are the areas not covered by the model or water deeper than 100 m.

Eutrophication indicators PSA & EUTRISK The conceptual model PSA No  High  Surface Physics Bottom Physics = Oxygen availability (C_kz_b + 0.5*C_oxy_sat)/1.5 Bottom diffusivity Stratification Low Yes  Dominant factors = Potential primary production (C_kz_b + C_oxy_sat + C_strat + C_adv)/4 (C_kz_b + C_oxy_sat + C_strat + C_blt)/4 (C_adv + C_strat)/2 EUTRISK Surface phytoplankton biomass Advection = Oxygen consumption Organic matter Following the principle of the dominant factor, three formulations of the bottom physics index are used () ; the numbers allocated to each index indicate their use in C_phys_bott. C_kz_b is the bottom diffusivity index, C_oxy_sat is the oxygen saturation index, C_strat is the stratification index, C_adv is the advection index and C_blt is the benthic layer thickness index.

Eutrophication indicators 1- SeaWiFS Chl-a June 2000 2- Export of Chl-a with the monthly-mean advection Vs=4m/d The export of the organic matter 3- Sum while re-sampling on the model grid Chl a (mg m -3 ) Adriatic Sea

Eutrophication indicators Adriatic Sea North Sea The export of the organic matter 0.65 * Log10 (Chl-a * deg + 1)

Eutrophication indicators North Sea Adriatic Sea Eutrophication Risk index EUTRISK Where are the most probable bottom oxygen deficiencies in August 2000 Lowest monthly dissolved oxygen concentration - 0 mg/l - 2 mg/l - 7 mg/l - 5 mg/l Eutrophic Hypertrophic Mesotrophic Oligotrophic Ecosystem status The Eutrophication Risk index (EUTRISK) represents the most probable oxygen deficiency distribution near the bottom integrating physical modelling and satellite remote sensing estimate of chlorophyll-a, the latter being considered as the main source of organic matter. The EUTRISK separates strongly eutrophicated ecosystems (anoxia events) from resisting eutrophicated ecosystems (biological stress by oxygen hypoxia), and from meso- and ologotrophic ecosystems.

Eutrophication indicator EUTRISK -Validation Dissolved Oxygen (mg/l) at the Bottom July-August 1994 (Souvermezoglou and Krasakopoulou, 1999) and EUTRISK in August 1999 Northern Adriatic Sea 2 5 4 3 3.5 4.5 - 0 mg/l - 2 mg/l - 7 mg/l - 5 mg/l Lowest monthly dissolved oxygen concentrations Note that the in situ measurements were done in 1994 and the EUTRISK is for 1999.

Eutrophication indicator EUTRISK -Validation August 8th August 13-14th August 18th August 24th August 4th Monitoring stations (pink dots and lines) 4-8-13-14-18-24 August 1998 (ARPA) Bottom oxygen (white lines): hypoxia <2 mg/l (dashed) anoxia (solid) EUTRISK - August 1998 - 0 mg/l - 2 mg/l - 7 mg/l - 5 mg/l Lowest monthly dissolved oxygen concentrations Note that the in situ measurements were done in 1994 and the EUTRISK is for 1999.

Eutrophication indicator EUTRISK - Validation Minimum of bottom oxygen measurement (NERI ) and (1-EUTRISK)*10 August 2000 & September 1999 >4 mg/l 2-4 mg/l 0-2 mg/l Danish Waters The agreement is generally good, therefore underestimations can be found in areas where the model resolution (20 km) is too low to reproduce the physics at local scale (like in enclosed bays or straits).

Eutrophication indicators PSA & EUTRISK Limitations No cover for waters: of the first nautical mile extremely shallow (Z90=1/Kd) deep (>100 m) - surface chl-a concentrations ~ primary production (C/Chl-a ratio, Irradiance, mixed layer depth) temporal resolution poor model resolution degradation of the remote sensing resolution index approach

Eutrophication indicators PSA & EUTRISK Further improvements and extensions - Improvement of the model resolution (from 20 km to 4-8 km), Interpolation of the physical variables to the SeaWiFS grid at 2 km, - Input of daily SST data at 2 km, Extension of the methodology to all European coastal seas, - Introduction of a more complete set of physical parameters, - Modelling of the nitrogen and oxygen cycles. u,v bottom layer + w + Irr0